Space - You Know Rocket Nozzles
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- Опубліковано 18 сер 2023
- The complicated parts of rocket engines get a lot of attention, but the design of the rocket nozzle has a big impact on the performance of the rocket.
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I'm really glad I found out about this underrated channel. Educational and straight to the point. It's a shame this channel doesn't have more subscribers.
I keep providing links to this channel when I'm on other forums. Even in the Comments section on other YT channels I refer to this by channel name & title. Hopefully this helps. In the mean time, I'm always grateful that I finally understand a concept that's otherwise escaped me. I've had a couple of things explained here that I was dying to have explained or seen an idea validated.
I see eager space , I click !
A couple of nitpicks:
19:03 mN -> millinewtons, MN->MegaNewtons
Also, Stoke Space is going with an aero-spike style design.
Always a good day when I find a cool channel like this. I'll spread the word.
I'm glad you brought up the rs25 when talking about flow separation. When you talked about needing an example to show flow separation, I thought about the rs25 that instant. Then it popped up on screen. Thank you
I love that video. Holy cow that nozzle is ringing....
0:02 I think this is one of those times the fact that the spaceflight community is very close-knit / insular rears its head. I would think that few people not well versed in rocket engines actually notice powerheads, since they'd gloss over it as just "stuff that connects the engine to the rocket". Nozzles are more immediately evocative to the layman of a rocket engine
Clear, concise, interesting -- this is consistently excellent content!
Aerospikes have 2 fundamental issues and a 1 circumstancial issue.
the first issue is cooling and everyday astronaute explaines it. Essentially at the point were the exhaust is going to transfere the most heat, the neck the surface area is going to be at least double and generally much more than that of a bell nozzle making cooling a challenge. It could be an advantage on expander cycles where the extra heat flux can be used to power more powerful pump and over come some of le limits of the expander cycle.
The second has been presented in one of stoke aerospace videos. The other issue of the aerospike is if you are wanting to have a high expantion ratio you need the exit to have a wide diameter also be ridiculously thin making the manufacturing tricky at best.
Finally for the circumstancial issue, the advantage of the aerospike is present when you need a single engine to be efficient in the variety of air pressures. But this can also be achieved to a degree by having multiple type of engine like we have today with staging. So unless you are going to do single stage to orbit, the aerospike doesn't really provide an advantage.
The other case which is a relatively new requirement, is propulsive landing on earth. For that only starship and stoke aerospace are the only ones doing anything about it.
Stoke have the upper stage engine which sort of behaves like an aerospike in a vaccum althoughb it wasn't designed with that in mind and like an normal engine and spaceX needed small engines for thrust vector control which could double as landing engines.
Thanks for adding all that info.
25:00 $415 for a lawn-watering pacifier? Dude, you'll never get consistent congressional approval for that. You need a $415 million research project in a district with high-seniority senators for a headline-grabbing holy grail this changes everything HYDROSPIKE lawn nozzle!
Maybe I can get an angel investor so I can hire some lobbyists to do that.
Reminds me of ARCAspace.
@@geryz7549I've thought about doing a video on them but I just don't know how to do it justice.
While I certainly wish to see this channel be successful in gaining subscribers and whatever the creator intends for it, I must admit I kinda like the feeling of being tuned in to this highly underrated source of Secret Space Stuff. :)
Thanks for the videos, really great stuff for the keen armchair enthusiast!
8:00 If I understand this correctly, flow separation occurs if the engine isn't at full power - and this is why it's difficult to throttle an engine down, or to throttle it down too far.
Also, I finally understand what that fat-skinny python is that wraps around the F-1 and Merlin nozzles. Thanks! It tapers down from the top because as it goes around more and more of the exhaust gas has exited into the nozzle and thus the remaining gas has to be squeezed into a smaller diameter tube so there's enough pressure at the last few holes for the gas to enter the nozzle, right?
There are a number of reasons throttling is hard, but that is one of them.
And yes, that's why the duct keeps getting smaller.
didn't know the rl10 had such relatively low chamber pressure at 44 bar.. yet it has the highest isp.. I assumed pressures had a more direct relationship with isp efficiency..
Expander cycle generally gets you pretty good efficiency. The RL-10 benefits a lot from having a full vacuum nozzle on it; note that the RS-25 with an 80:1 nozzle is about as efficient as an RL-10 with a 130:1 nozzle. And the new RL-10 will get up to an Isp of 465 with a really big expandable nozzle (280:1).
Where it falls down is the thrust that it has is pretty low - only about 110 kN. That's about 1/10th of the Merlin 1D Vacuum, and that means if you want to fly the RL-10 in a second stage (like Atlas V), you need to have a big first stage that tosses it very high because the RL-10 doesn't have enough thrust to both counter gravity and accelerate to orbital speed. Once you get into orbit where lower thrust is less of a disadvantage it's a much better engine.
It's also reportedly anywhere from $10-20 million a pop in small quantities.
@@EagerSpace if only someone could produce a medium thrust hydro/lox engine of any cycle and offer it for less than 15million.. like we had 50 years ago with the j2's.. it would fix this huge gap in the thrust discrepancies.. I doubt it would take long to find a happy buyer
Excellent!!
Many thanks!
How would someone calculate the inefficiency of a boister engine optimized for a specific altitude? Are such engines always optimized for sea level, or somewhere in the lower atmosphere in practice?
Doing the calculations goes into the "physics is complicated" part, but there are design tools where you can put in your engine parameters and it will spit out the performance numbers.
For boosters engines, the number of engines you can fit under the booster is constrained by the size of the powerhead, and then you put on a nozzle that works with that spacing. A little bigger is better from an efficiency standpoint, and with tight packaging the nozzle size is small enough that you don't worry about flow separation.
If you look at booster engines you'll see that the nozzle diameter is pretty close to the power head diameter.
The world is maybe a bit different if you buy your engines, in which case you're stuck with the dimensions of the engine you buy, and then the diameter of the first stage may be set by the nozzle size.
That was fun.
Excellent presentation of rocket nozzle design!
Love you vids, shame you don't have more subs although that being said, I think it is likely that the people who do watch your videos dispropitionately enjoy/learn from them.
I'm still a couple years off from my mechanical engineering degree, But why is it important what happens to the exhaust gasses after it's evacuated the nozzle? It would seem that as long as the mass is traveling in the correct direction as it exits the nozzle, it doesn't matter what happens to it afterword. What am I missing?
I'm going to oversimplify here - you can dig into the original references which IIRC have plenty of differential equations to make you happy...
It *is* all about the exhaust gas going in the correct direction, but it only goes in the correct direction if (to a first order approximation) the pressure in the nozzle is the same as the pressure outside. If the pressure is higher - the underexpanded case - you could have gotten more work out of the exhaust if you gave it a bigger nozzle to expand against, since it's going sideways out of the nozzle rather than toward the back
@@EagerSpace Oh ok! So having expansion outside the nozzle Is like leaving work on the table. By having a larger nozzle and containing that expansion we can do more work i.e. a higher velocity exhaust. Did I get that right?
I sure love my differential equations xD
@@EagerSpaceI thought that the question was why do vacuum engines get better ISPs whenever their nozzles are under expanded and the angle of ejection are never as ideal than sea level engines?
I might be completely wrong about this but when you look at shock diamonds in low altitudes versus booster engine exhaust separation at high altitudes one would assume that the shock diamonds were the more efficient of the two extremes . . .🤔
I have a few hose nozzles I got at the dollar store this summer. Can I send you one of those?
Does it have saving card buckle?
4:28 hasn't rocket lab said Rutherford has a chamber pressure of about 50 bars?
100 bar was the value I've found but I didn't find anything official so that could be incorrect.
And it's possible that they started at a lower chamber pressure and upgraded later on.
@@EagerSpace here's where i got the 50 bars from, ua-cam.com/users/liveZw3sIUyfSfc?feature=share&t=736 posted just 2 years ago by rocket lab (also you were right on the money for the vacuum expansion ratio btw)
@@detective_yetiThanks for the link.
👍🏻👍🏻👍🏻🙏🏻
I could design better such as uranium gas core fission fragment and also consider how Japan Nitrogen of early 1940s Hamgyong Province was perfecting cryogenic deuterium fueled rocket plane
engines for Alvarez to be credited for muon catalyzed so if interested I can furnish MIT peer reviewed information.
Pangea aerospike?
I thought about including Pangea, but I just couldn't find any detailed information about what they are doing. They have the P1 that apparently works but they don't give any information on what engine cycle it uses, how much it weighs, how big it is, and what specific impulse they are getting. They're working on a 300 kN engine but there is also pretty much no useful information there.
I'm not sure who their market is. Electron is the only smallsat launcher actually flying and they have the whole market at 300kg to orbit and aren't as busy as they hoped. It's not clear that anybody is aiming between Electron and Falcon 9 as some of the other companies have moved upscale, and it's also not clear if anybody with those aspirations is looking for an engine. But I'm not well versed on what is going on in Europe and there could easily be opportunities there.
I would be happy to see a production aerospike as that would at least presumably give us some real numbers.
From my look into them I still can’t tell you what the performance was, but it probably wasn’t very good. Those guys just wanted to get their engine running, and a lower pressure would be convenient for that. The throat annulus is also wide, and we can see in their material that the exhaust almost immediately turns outwards, so the expansion ratio is low and it can’t use very effectively the purported advantage of an aerospike.. Given its status as a demo article, I believe it was pressure-fed. Why bother building pumps if you’re just trying to demonstrate that you can make a nozzle in that shape, you know? But I don’t know that for sure.
@@ryanrising2237The information I found said the XRS-2200 was a gas-generator design. I don't think there is any way that X-33 could afford the weight of pressure-fed tanks.
@@EagerSpace that’s totally correct - XRS-2200 was gas-generator. I was referring to Pangea’s DemoP1 aerospike thrust chamber.